Switching method and switch device

Abstract

A switch device has an object ID rewrite unit and a file access control unit. The object ID rewrite unit, when an original object ID is contained in a reply to be transferred, rewrites the original object ID to an information entraining object ID by inserting server identification information into the original object ID, while when the information entraining object ID is contained in a reply to be transferred, restores the information entraining object ID to the original object ID. The file access control unit includes a table for managing a combination of address information of a server and server identification information, estimating address information of a server corresponding to sever identification information contained in an information entraining object of a request to be transferred with reference to the table, and determines a destination of the request on the basis of the address information.

Description

[0001] 1. Field of the Invention[0002] The present invention relates to a switch logically disposed between a client and a server, and more specifically to a switch which is disposed in a client server system in which a remote file system is implemented for executing file processing through a network, and provides a single system image (SSI) transparent to the client and network traffic control such as load distribution.[0003] 2. Description of the Related Art[0004] As a method for realizing a client server system through a network a famous method is known, which employs a network file system (NFS) protocol disclosed in RFC (Request For Comments) 1094 and RFC 1813. The NFS protocol provides basic operations as a file system such as creation, deletion, read / write operation, movement and the like of a file for a server located at a remote place through a network, and convenience such as sharing of files with other clients. In the NFS protocol, a client employs an object ID for identif...

AI Technical Summary

Benefits of technology

[0042] Finally, in accordance with the present invention, provided that a client and a server support only a file system service protocol (e.g., NFS) mediating a standard network, an SSI file service can be realized for a client by integrally controlling a plurality of servers without modifying existing systems. Upon implementation of the switch device of the present invention, it is sufficient to only dispose the switch device logically between a client and a server, because any alteration of processings for the client and the server such as setting of IP alias and introduction of a virtual distributed file system is unnecessary.

[0043] The present invention can execute processings in a transparent fashion to a client when an administrator executes an operation not originally required to inform a client such as purposes of a load and of capacity distribution, for example when the administrator moves an object from a server which is once allocated to another server, and hence it can keep consistency of the SSI session presented to the client. The switch device of the present invention can bring into correspondence an object ID for specifying objects such as a directory and a file and a server for processing the object, and converts new and old object IDs. When the object is moved to be transparent to the client, and can distribute, on the basis of the result, a request from the client to a proper server and a reply containing an object ID from the server to a proper client.

[0044] The present invention is capable of processing a greater amount of object IDs without the use of the retrieving operation, and of transferring a packet to a proper server, and is hence advantageous for making processings a high speed and hardware implementation.

[0045] The present invention is capable of shortening time for a name solving processing by distributing a load of the name solving processing to a server and a switch device. The switch device of the present invention includes a pseudo file system, which system controls only a mount point and is capable of transferring name solving under the mount point to each server without contradiction.

[0032] In accordance with the switch device according to the present invention, the switch device includes a switch capable of bring into correspondence a server for managing an object and an object ID of the just-mentioned object, and provides the object ID transmitted to the client with identification information of a server for managing the object. With such arrangement, when the client tries to access its object in succession, server identification information for controlling the object is contained in an object ID in a request transmitted by the client, so that the switch device can determine a server of a destination from the server identification information contained in the request. Accordingly, application of the switch device of the present invention eliminates the need of specifying the server for managing the object on the side of the client, so that transparency to the client can be realized.

[0047] In the present invention, when use can be made of tag information at the layer 4 or lower of the OSI reference model, rewriting of an object ID is ensured with a hardware using those pieces of tag information, and hence the processings are made a further high speed.

[0048] Further, in the present invention, even upon an object relocation work between servers by a controller the relocation work is masked to a user, whereby a control work can be executed without causing system interruption and file access service interruption.

Problems solved by technology

(1) Even a method employing a layer 4 to 7 switch and even a method employing virtual IP clustering suffer from a difficulty that contents rewritten upon redirection of a packet are limited to a MAC address or an IP address. For this, when in a protocol in which a client stores an object ID such as a file handle of NFS in a cache, an administrator executes an operation which does not require the need of informing a client for the purpose of load distribution and capacity distribution, for example when an object is moved from a server once allocated to a client to another server, the client accesses the server while accommodating an object ID of an old server in the packet. Accordingly, even though the switch transfers the packet to a new server, the new server fails to read the object ID in the packet and sends back an error to the client. More specifically, in the file system service mediating a load distributed network, transparency to the client can not been realized even when a conventional method of load distribution is applied;

(2) There is essential an improvement for a file server which is already utilized by a user upon setting the IP alias and introduction of the virtual distributed file system. Accordingly, when a file system of an existing client server is operated, for obtaining convenience provided while intactly utilizing a construction of the foregoing client server complicated installation work happens even when only a purpose of the load distribution is solved.

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